rotation in right to left contexts

[davidcarlisle]

Brief outline of the bug

this is essentially a copy of

latex3/babel#42

but restricted to the core rotation issues.

\documentclass{article}


\usepackage{graphics}

\begin{document}


x\fbox{\rotatebox{90}{abc}}

\ifx\textdir\undefined\else
\textdir TRT 
\fi

\ifx\beginR\undefined\else
\TeXXeTstate=1
\leavevmode\beginR
\fi
x\fbox{\rotatebox{90}{abc}}y

\end{document}

In luatex you get

in xetex you get

and in pdftex you get

pdfTeX warning: pdflatex: \pdfrestore: missing \pdfsave

!pdfTeX error: pdflatex: 1 unmatched \pdfsave after page shipout
 ==> Fatal error occurred, no output PDF file produced!

[davidcarlisle]

It is rather under-specified whether the default centre of rotation is the left hand edge or the right hand edge (actually it is specified in several places that it is the left, but it is implicitly implying left-to-right writing direction)

If we assume that the centre should be the start of the baseline in the writing direction then \rotatebox{90}{..} will come mostly below the baseline in a RTL context. In luatex this I think gives the desired output if we take that interpretation,

\documentclass{article}


\usepackage{graphicx}

\makeatletter
\protected\long\def\STDrotatebox#1#2{%
  \leavevmode
  \Grot@setangle{#1}%
  \setbox\z@\hbox{{#2}}%
\ifnum\textdirection=\z@
  \Grot@x\z@
\else
  \Grot@x\wd\z@
\fi
  \Grot@y\z@
  \Grot@box}

\long\def\Grot@box@std#1#2{%
  \Grot@setangle{#1}%
  \setbox\z@\hbox{{#2}}%
\ifnum\textdirection=\z@
  \Grot@x\z@
\else
  \Grot@x\wd\z@
\fi
  \Grot@y\z@
  \Grot@box}
\long\def\Grot@box@kv[#1]#2#3{%
  \@begin@tempboxa\hbox{#3}%
    \Grot@x\width \divide\Grot@x\tw@
    \Grot@y\height \advance\Grot@y-\depth \divide\Grot@y\tw@
    \setkeys{Grot}{#1}%
    \setbox\z@\box\@tempboxa
    \Grot@setangle{#2}%
    \Grot@box
  \@end@tempboxa}


\def\Grot@box{%
  \begingroup
  \CalculateSin\Grot@angle
  \CalculateCos\Grot@angle
  \edef\Grot@sin{\UseSin\Grot@angle}%
  \edef\Grot@cos{\UseCos\Grot@angle}%
%   \GDebug{Rotate: angle \Grot@angle, sine is \Grot@sin,
%             cosine is \Grot@cos}%
  \Grot@r\wd\z@  \advance\Grot@r-\Grot@x
  \Grot@l\z@     \advance\Grot@l-\Grot@x
  \Grot@h\ht\z@  \advance\Grot@h-\Grot@y
  \Grot@d-\dp\z@ \advance\Grot@d-\Grot@y
  \ifdim\Grot@sin\p@>\z@
    \ifdim\Grot@cos\p@>\z@
      \Grot@Py\Grot@height \Grot@r\Grot@h%B
      \Grot@Px\Grot@right  \Grot@r\Grot@d%E
      \Grot@Px\Grot@left   \Grot@l\Grot@h%C
      \Grot@Py\Grot@depth  \Grot@l\Grot@d%D
    \else
      \Grot@Py\Grot@height \Grot@r\Grot@d%E
      \Grot@Px\Grot@right  \Grot@l\Grot@d%D
      \Grot@Px\Grot@left   \Grot@r\Grot@h%B
      \Grot@Py\Grot@depth  \Grot@l\Grot@h%C
    \fi
  \else
    \ifdim\Grot@cos\p@<\z@
      \Grot@Py\Grot@height \Grot@l\Grot@d%D
      \Grot@Px\Grot@right  \Grot@l\Grot@h%C
      \Grot@Px\Grot@left   \Grot@r\Grot@d%E
      \Grot@Py\Grot@depth  \Grot@r\Grot@h%B
    \else
      \Grot@Py\Grot@height \Grot@l\Grot@h%C
      \Grot@Px\Grot@right  \Grot@r\Grot@h%B
      \Grot@Px\Grot@left   \Grot@l\Grot@d%D
      \Grot@Py\Grot@depth  \Grot@r\Grot@d%E
    \fi
  \fi
  \advance\Grot@height\Grot@y
  \advance\Grot@depth\Grot@y
  \Grot@Px\dimen@  \Grot@x\Grot@y
  \Grot@Py\dimen@ii \Grot@x\Grot@y
  \dimen@-\dimen@     \advance\dimen@-\Grot@left
  \dimen@ii-\dimen@ii \advance\dimen@ii\Grot@y
%   \GDebug{Rotate: (l,r,h,d)^^J%
% Original \the\Grot@l,\the\Grot@r,\the\Grot@h,\the\Grot@d,^^J%
% New..... \the\Grot@left,\the\Grot@right,%
%          \the\Grot@height,\the\Grot@depth}%
  \setbox\z@\hbox{%
    \kern\dimen@
    \raise\dimen@ii\hbox{%
\ifnum\textdirection=\z@\else
\typeout{[\the\Grot@left][\the\Grot@right][\the\dimen@]}%
\kern\dimexpr\Grot@right-\dimen@\relax
\raise-\dimen@ii\hbox
\fi
{\Grot@start\box\z@\Grot@end}}}%
  \ht\z@\Grot@height
  \dp\z@-\Grot@depth
  \advance\Grot@right-\Grot@left\wd\z@\Grot@right
  \leavevmode\box\z@
  \endgroup}

\makeatother

\begin{document}


a\fbox{\rotatebox[origin=Br]{90}{abc}}

1\fbox{\rotatebox{45}{abc}}
2\fbox{\rotatebox{90}{abc}}
3\fbox{\rotatebox{-45}{abc}}
4\fbox{\rotatebox{-90}{abc}}


\ifx\textdir\undefined\else
\textdir TRT 
\fi

a\fbox{\rotatebox[origin=Br]{90}{abc}}

1\fbox{\rotatebox{45}{abc}}
2\fbox{\rotatebox{90}{abc}}
3\fbox{\rotatebox{-45}{abc}}
4\fbox{\rotatebox{-90}{abc}}


\end{document}

[u-fischer]

Origin = Bl doesn't look right. And perhaps one would need origins s and e for start and end in writing direction (so s=l in TLT and r in TRT).

\documentclass{article}


\usepackage{graphicx}

\makeatletter
\protected\long\def\STDrotatebox#1#2{%
  \leavevmode
  \Grot@setangle{#1}%
  \setbox\z@\hbox{{#2}}%
\ifnum\textdirection=\z@
  \Grot@x\z@
\else
  \Grot@x\wd\z@
\fi
  \Grot@y\z@
  \Grot@box}

\long\def\Grot@box@std#1#2{%
  \Grot@setangle{#1}%
  \setbox\z@\hbox{{#2}}%
\ifnum\textdirection=\z@
  \Grot@x\z@
\else
  \Grot@x\wd\z@
\fi
  \Grot@y\z@
  \Grot@box}
\long\def\Grot@box@kv[#1]#2#3{%
  \@begin@tempboxa\hbox{#3}%
    \Grot@x\width \divide\Grot@x\tw@
    \Grot@y\height \advance\Grot@y-\depth \divide\Grot@y\tw@
    \setkeys{Grot}{#1}%
    \setbox\z@\box\@tempboxa
    \Grot@setangle{#2}%
    \Grot@box
  \@end@tempboxa}


\def\Grot@box{%
  \begingroup
  \CalculateSin\Grot@angle
  \CalculateCos\Grot@angle
  \edef\Grot@sin{\UseSin\Grot@angle}%
  \edef\Grot@cos{\UseCos\Grot@angle}%
%   \GDebug{Rotate: angle \Grot@angle, sine is \Grot@sin,
%             cosine is \Grot@cos}%
  \Grot@r\wd\z@  \advance\Grot@r-\Grot@x
  \Grot@l\z@     \advance\Grot@l-\Grot@x
  \Grot@h\ht\z@  \advance\Grot@h-\Grot@y
  \Grot@d-\dp\z@ \advance\Grot@d-\Grot@y
  \ifdim\Grot@sin\p@>\z@
    \ifdim\Grot@cos\p@>\z@
      \Grot@Py\Grot@height \Grot@r\Grot@h%B
      \Grot@Px\Grot@right  \Grot@r\Grot@d%E
      \Grot@Px\Grot@left   \Grot@l\Grot@h%C
      \Grot@Py\Grot@depth  \Grot@l\Grot@d%D
    \else
      \Grot@Py\Grot@height \Grot@r\Grot@d%E
      \Grot@Px\Grot@right  \Grot@l\Grot@d%D
      \Grot@Px\Grot@left   \Grot@r\Grot@h%B
      \Grot@Py\Grot@depth  \Grot@l\Grot@h%C
    \fi
  \else
    \ifdim\Grot@cos\p@<\z@
      \Grot@Py\Grot@height \Grot@l\Grot@d%D
      \Grot@Px\Grot@right  \Grot@l\Grot@h%C
      \Grot@Px\Grot@left   \Grot@r\Grot@d%E
      \Grot@Py\Grot@depth  \Grot@r\Grot@h%B
    \else
      \Grot@Py\Grot@height \Grot@l\Grot@h%C
      \Grot@Px\Grot@right  \Grot@r\Grot@h%B
      \Grot@Px\Grot@left   \Grot@l\Grot@d%D
      \Grot@Py\Grot@depth  \Grot@r\Grot@d%E
    \fi
  \fi
  \advance\Grot@height\Grot@y
  \advance\Grot@depth\Grot@y
  \Grot@Px\dimen@  \Grot@x\Grot@y
  \Grot@Py\dimen@ii \Grot@x\Grot@y
  \dimen@-\dimen@     \advance\dimen@-\Grot@left
  \dimen@ii-\dimen@ii \advance\dimen@ii\Grot@y
%   \GDebug{Rotate: (l,r,h,d)^^J%
% Original \the\Grot@l,\the\Grot@r,\the\Grot@h,\the\Grot@d,^^J%
% New..... \the\Grot@left,\the\Grot@right,%
%          \the\Grot@height,\the\Grot@depth}%
  \setbox\z@\hbox{%
    \kern\dimen@
    \raise\dimen@ii\hbox{%
\ifnum\textdirection=\z@\else
\typeout{[\the\Grot@left][\the\Grot@right][\the\dimen@]}%
\kern\dimexpr\Grot@right-\dimen@\relax
\raise-\dimen@ii\hbox
\fi
{\Grot@start\box\z@\Grot@end}}}%
  \ht\z@\Grot@height
  \dp\z@-\Grot@depth
  \advance\Grot@right-\Grot@left\wd\z@\Grot@right
  \leavevmode\box\z@
  \endgroup}

\makeatother
\begin{document}


a\fbox{abc}\fbox{\rotatebox[origin=Br]{90}{abcrr}}\fbox{\rotatebox[origin=Bl]{90}{abcll}}

\ifx\textdir\undefined\else
\textdir TRT
\fi

a\fbox{abc}\fbox{\rotatebox[origin=Br]{90}{abcrrr}}\fbox{\rotatebox[origin=Bl]{90}{abclll}}

\end{document}

[davidcarlisle]

yes I hadn't really checked the interpretation of all the origin options, just forced that example to work to see if that is the expected answer rather than rotating from the left edge.

[car222222]

Another thing to resolve: since TRT is a reflection of TLT, should the meaning of a ‘positive rotation value’ also get reflected to mean ‘clockwise’ (assuming Hebrew clocks look like (most) English clocks).

It’s all relative:-).

[car222222]

Why not rotate about the centre of the box? I recall ‘discussing’ this with Sebastian, who maintained volubly that it was ‘completely obvious’ what a rotation is, so no need to specify the centre!

[davidcarlisle]

should the meaning of a ‘positive rotation value’ also get reflected to mean ‘clockwise’

Unless there is strong push from native speakers that that is the convention I think it would be pretty confusing to change the direction.

Why not rotate about the centre of the box?

I don't think we can change the behaviour of LTR documents. The centre is the default value of the origin key so \rotatebox[]{90}{1234} rotates around the centre, as does \rotatebox[origin=c]{90}{1234}

[davidcarlisle]

We also need to coordinate with the patches done for xetex by the bidi package.

\documentclass{article}


\usepackage{graphicx,bidi}
\TeXXeTstate=1


\begin{document}


a\fbox{\rotatebox[origin=Br]{90}{abc}}

1\fbox{\rotatebox{45}{abc}}
2\fbox{\rotatebox{90}{abc}}
3\fbox{\rotatebox{-45}{abc}}
4\fbox{\rotatebox{-90}{abc}}



\setRTL

a\fbox{\rotatebox[origin=Br]{90}{abc}}

1\fbox{\rotatebox{45}{abc}}
2\fbox{\rotatebox{90}{abc}}
3\fbox{\rotatebox{-45}{abc}}
4\fbox{\rotatebox{-90}{abc}}


\end{document}

[vinoruto]

@davidcarlisle

Unless there is strong push from native speakers that that is the convention I think it would be pretty confusing to change the direction.

If it is of any help, I am a native speaker of Arabic (A Right to left language), however, I do not have much experience regarding the programming aspect you are discussing, I am not used to modifying packages.

[car222222]

A use-case for rotating text (the only generic one I can immediately think of):

Typesetting column headings in a table, if they are long one often rotates them through 90deg (or 45deg for easier reading).
Now think about an RTL document. My intuition is that the “equivalent layout” of a table in RTL is obtained by a reflection. For such headings is thus obtained by rotating the text through the opposite angle.

[car222222]

I think that considering the centre of rotation is not helpful in practical use-cases.
It is better to think as follows: first rotate the box (about any centre); then decide where
on the page you want the reference of the “new box” to be.
Note: “new box” needs interpretation, it could be the rotated box itself, or the bounding box of the rotated box.

[car222222]

@vinoruto Did you follow my use-case regarding rotated text in column-headings? Your input on this would be useful.

@davidcarlisle or @u-fischer Any chance of producing the two possibilities for such a table? Preferably using 45deg rotation as this makes the distinction very clear.

This is not entirely a question of programming although I can see arguments (at least from non-tech types) for not changing the meaning of a “positive rotation”. But therefore there is probably a need to be able to specify (at document level) the direction of a rotation that is relative to the current text direction, rather than absolutely (relatively to the page co-ordinate system].

[vinoruto]

@car222222

Did you follow my use-case regarding rotated text in column-headings? Your input on this would be useful

It is more appropriate for me if there is a worked example, I can provide sample text if you need so.

[car222222]

I asked if @davidcarlisle or @u-fischer can make up, or find, examples of my use-case.
But they are very busy people. Maybe I shall loook for something I can adapt.